Absolutely home buyers should be concerned about molds in their prospective home.  Especially when a good home inspector informs them that there are conditions in the house that may produce future out breaks of mold.   Maybe there is a bargain to be had in the real estate transaction.  A possible diamond in the rough provided the savvy buyers can identify the causes of the mold and prevent future outbreaks.

Lets start at the beginning.

The public image of mold is often misleading and far from the truth.  And yes, certain molds are toxic to humans especially if the individual is sensitive or allergic to molds.   However, keep in mind that molds are a large class of organisms that serve a very important function in the environment – they decompose and break organic matter as part of the nutrient cycle.  They break down fallen leaves from trees and other detritus.  Think of the mold that magically appears and grows on our bread if left uneaten for too long.

Molds are ubiquitous.  They can be found in our cars, between our toes, the spores can be found floating in the air.  The key to mold growth in our homes is a source of moisture and organic matter and humid environment, anything over 65% humidity will support mold.

Where are molds most commonly found in the home?

In short, mold can be found anywhere in the home provided there is a constant source of moisture, poor ventilation situation and organic surface for mold to feed on.   It is even possible for mold to grow on dust covered surface where mold feeds on the dust.

Here is an example that mold can be found any where in the house, and in this case at the bottom of the drywall next to the hot water tank. Guess where the moisture source came from. Hint : look at the temperature pressure relief valve (TPV).

Molds are often found in bathrooms because we have a source of moisture when we shower, a condition for poor ventilation and hence the humidity especially in the winter when we close the windows to keep the heat inside.  And, we have a source of organic matter – the drywall, particularly around the ceiling because hot humid air tends to rise and hangs out at the ceilings when there is a lack of proper ventilation.   Bathrooms are required to have either a window accessible to the exterior or mechanical ventilation to the exterior with a minimum of 50 cubic foot per minute (cfm)  exhaustion.  It is highly recommend that after a shower, to leave the bathroom exhaust fan on for about 30 minutes to complete vent the humid air to the exterior.  A simple timer installed on the exhaust fan will handle that.

Other common areas to find mold is the basement or crawl spaces and attic spaces.    The scent of musky dampness is a very good indicator that the environment has poor ventilation and highly likely will have mold somewhere.  Often mold is growing behind wood panels, organic surfaces near the floor where the moisture is highest.  In the attic, mold will grow right on the wood framing member and roof sheathing.

Here is an exhaust vent from the kitchen discharging into the attic. Note the growth of mold on the roof sheathing.

What all these places have in common is they have poor ventilation and a source of moisture.  Basements and crawlspaces are often damp to begin with.  The moisture comes from the ground as the foundation is made of cement which is porous.    Efflorescence is a good indicator that moisture has moved from inside the cement and onto the surface of the cement.   Attics with improper vent discharges often will result in mold growth.   For example, bathroom vents, kitchen vents and even dryer vents can be improperly installed to discharge into the attic space instead of directly to the exterior.  These vents exhaust moist indoor air supplying the attic with enough moisture to to support mold growth.

Cracks in the foundation floor. Efflorescence (white mineral deposits) indicates that water has been moving through the cracks.

Mold is also commonly found in rooms that have an exterior wall where it can be cold during the winter season with insufficient or missing insulation.  When the heat is turned on, warm air passes over the cold surface, often the cold corner of a room where the ventilation is poor, the warm air forms condensation on top of the cold surface.  This provides enough moisture to support mold growth around those cold corners of the room.  To remedy this is simple, ventilate the room.  Make sure enough air is circulating the room and insulate the attic and exterior walls to rid the house of those cold corners.

The thermogram shows the cold spots along the framing members and corners of the room due to thermal transfer. With poor ventilation, mold can often be found growing on the top corners of rooms with exterior walls during winter season.

What you should know to get rid of mold in the house.

A good home inspector will be able to explain in detail and in layman terms to their clients what they need to know about mold should the buyers wish to continue with the real estate transaction.       What can be done? – depends on the extent of the damage.  First, address the root cause.  Where is the moisture coming from?  Eliminate the source of moisture.  Next remove and replace all affected building materials.  Ensure there is adequate ventilation in the new construction.

If the extent of the damage includes structural members, this is where it is having such information is priceless as prospective buyer can determine financially if they which of continue, renegotiate the price or walk away from the real estate transaction.  If the home buyer decides to proceed with the purchase, they should be fully aware of the risks involved.  A good home inspector needs to explain in laymen terms the implications of the risk factors noted.  Every risk factor requires a detail explanation to the client.